The purpose of this study was to investigate the noise properties and levels of common noise sources in a neonatal intensive care unit (NICU) and in particular inside and around an incubator. Many previous studies have been made on noise levels in NICU, frequently focusing on A-weighted sound levels. In this study it was not assumed that infant's hearing follows the same equal loudness curve as adults and hence instead of A-weighting, short time averaged sound spectra in the frequency range 20 Hz to 20 kHz was logged to identify the frequency distribution of specific noise generating events. It was seen that alarms and CPAP air-flow increased the noise level by up to 8 dB outside but was barely noticed inside when considering the un-weighted noise level. However, by analyzing individual frequencies, most events were noticeable inside the incubator. For instance, frequencies above 1 kHz were increased by 10 dB inside and 11 dB outside the incubator when CPAP was turned on. Opening and closing the incubator increased the un-weighted noise level by 8 dB inside and 7 dB outside.